1,720,985 research outputs found
Disassembling to design: a fundamental learning experience
No full textDisassembly refers to the act of taking something apart, often a piece of machinery, primarily for reuse. In product design, disassembly means analysing an object to understand its parts and characteristics. Despite its broader potential, disassembly in product design is often associated exclusively with sustainability, reparability, and reuse strategies (Design for Disassembly, DfD). This article explores its value as a training and educational tool for young designers.
As products become more complex, and as knowledge of materials, manufacturing technologies and assembly techniques grows in importance, methods and tools for analysing existing products have been integrated into design education - disassembly being one of them. Examining everyday objects helps to deconstruct what Duncker defines as ‘functional fixedness’, the tendency to focus solely on the typical use of an object or one of its parts. Aligning with Kolb’s learning-by-doing approach, this article reflects on the benefits of incorporating hands-on exercises that enhance manual dexterity within educational programs.
The paper aims to investigate the skills developed through disassembly by identifying two levels of learning: a macro level, a technical and practical dimension, focusing on the skills acquired during the act of disassembly; and a micro level, a strategic and reflective dimension, concerning how disassembly shapes approaches to product design. Following an initial analysis of the literature and common applications of disassembly theories, the paper introduces a new perspective based on the results of a five-week design studio conducted with young designers in their early training phase. The different phases of the exercise, along with their content and outputs, will be discussed. Additionally, the educational value of disassembly and its broader implications for design will be examined to address the central question: how can disassembly improve product design and innovation while educating designers?
To address this question, the study proposes a possible categorization of disassembly values into:
i) disassembly for product understanding,
ii) disassembly as a method for deconstructing complex problems, and
iii) disassembly to foster lateral thinking. For each category, the theoretical foundations and educational implications will be summarized.
The article aims to demonstrate how disassembly can enhance the training of future designers by identifying key learning areas and defining their significance. To design a product, one must first understand its components and how they function. This requires analyzing each component individually, which, in turn, necessitates breaking down, or disassembling, the product. This study highlights the educational and training value of disassembly, emphasizing its role in fostering a more conscious and informed approach to design
Strutture ibride a bassa densità: alluminuri di nichel e nanotubi di carbonio per applicazioni ad alta temperatura
No full textQuesta attività di ricerca è focalizzata sullo studio dei metodi produttivi su scala di laboratorio di due differenti strutture ibride a bassa densità per applicazioni nel settore automotive, con lo scopo di valutare l’influenza di diversi parametri di processo sulle caratteristiche finali del materiale composito.
I materiali ibridi comprendono compositi con rinforzo mediante fibre o particelle, schiume e lattici, e quasi tutti i materiali naturali. L’interesse scientifico di questi materiali è orientato sulla loro capacità di combinare diverse proprietà, massimizzare l’efficienza strutturale, minimizzare il peso ed i costi di produzione.
In questo studio sono state analizzate due tipologie di materiali ibridi con differenti strutture ed applicazioni. Il primo materiale è un intermetallico, nello specifico un alluminuro di nichel, che viene prodotto attraverso sintesi per combustione (CS) attivata da microonde. Esso viene impiegato come elemento di giunzione fra materiali eterogenei, come inconel e titanio, e risulta essere adatto sia per riparare componenti in-situ sia per assemblare componenti con diverse caratteristiche, che devono essere contemporaneamente esposti ad ambienti, temperature o sforzi meccanici differenti. Il secondo è invece un composito nanostrutturato dove nanotubi di carbonio (CNTs) sono fatti accrescere, mediante tecnica di Chemical Vapor Deposition, su un substrato a matrice di carbonio rinforzato con fibre di carbonio. I benefici nell’impiego di tali strutture ibride risiedono nella possibilità di controllare il coefficiente di espansione termica del componente finale, migliorandone la resistenza all’usura, l’idrofobicità e la conducibilità termica. Grazie alla resistenza all’abrasione ad elevata temperatura, esso viene impiegato nel gruppo freno e/o frizione nel settore delle competizioni automobilistiche.
L’approccio analitico impiegato per lo sviluppo delle tecniche di sintesi dei due materiali sopra menzionati è differente. Nel caso degli alluminuri di nichel, lo scopo principale della attività è basato sullo sviluppo di un modello matematico predittivo della CS di polveri metalliche micrometriche innescata da microonde.
La simulazione ha accoppiato diversi moduli, in particolare chimico, termico ed elettromagnetico, al fine di ottenere informazioni altrimenti difficilmente misurabili per via sperimentale. In tal modo è possibile valutare sia la variazione composizionale e delle temperature sia la cinetica di reazione durante il procedere della sintesi, dimostrando come l’applicazione delle microonde durante e dopo la sintesi possa alterare la velocità di raffreddamento dei prodotti e, di conseguenza, la loro microstruttura. La CS è stata scelta come tecnica di giunzione grazie alla sua capacità di sfruttare reazioni chimiche fortemente esotermiche che, una volta innescate, si autopropagano fino a completo esaurimento delle specie reagenti. Inoltre grazie al riscaldamento a microonde, che si basa sul trasferimento di energia invece che sul trasporto di calore, una volta innescata la reazione, è possibile continuare a generare calore nei prodotti, riscaldandoli e minimizzando la zona termicamente alterata.
Nello studio dei compositi nanostrutturati si sono invece analizzati due differenti approcci sperimentali che permettessero la sintesi di CNT su un substrato a base carbonio; essi differiscono per la presenza o meno di uno strato intermedio tra componente e rivestimento. La crescita di CNT è un approccio promettente per migliorare le proprietà meccaniche, elettriche e termiche di compositi strutturali. Tuttavia, il presente lavoro costituisce solamente uno studio preliminare di una tematica più ampia nell’ambito dello sviluppo di un nuovo materiale composito, come l’ infiltrazione in resina e l’ottimizzazione di tale processo.The aim of the activity is focused on laboratory scale production methods of two different lightweight hybrid structures for high performance automotive application and on understanding the influence of several process parameters on the composite final characteristics.
Hybrid materials include composites reinforced by fibers or particles, foams and lattices, and almost all natural materials. The goals of hybrid structures are the combination of different material properties, maximization of structural efficiency, weight and costs reduction. In the present study two types of hybrid materials showing different structures and target applications were analyzed.
The first one is an intermetallic, in particular a nickel aluminide, produced through combustion synthesis (CS) activated by microwaves. This lightweight intermetallic is applied as joining material between heterogeneous base metals, like inconel and titanium, and it can also be used to in-situ repair damaged components and for assembling components presenting dissimilar characteristics, which need to be simultaneously exposed to different environments and/or temperature and/or mechanical stresses.
The latter is a nanostructured composite where carbon nanotubes (CNTs) are grown on substrates made of carbon matrix reinforced with carbon fibers, by means of chemical vapor deposition technique. The benefits expected from the use of CNT-containing hybrid structures are related to the possibility to control expansion coefficient of the final components, and meanwhile to improve wear resistance, hydrophobicity and thermal conductivity. Thanks to high wear resistance at elevated temperature carbon nanotubes are currently used for high performance brake and clutch manufacturing in automotive applications.
The two hybrid materials have been investigated using two different analytical approaches.
With respect to nickel aluminides, the main research purpose is focused on developing a predictive and mathematical model of microwave ignited and sustained CS of micrometric metal powders. The simulation couples chemical, thermal and electromagnetic models to overcome the difficulty, or impossibility, to perform non perturbative temperature measurements during microwave initiated CS. Numerical simulation is also used to estimate the heating and cooling rates in each portion of the reactants and products volume, as well as of the surrounding substrates and supporting materials. The CS process has been chosen as joining technique because is based on the highly exothermic reaction by reactants, which, if properly ignited, spontaneously turn into products. In addition the activation by microwave heating is particularly efficient because is based on energy transfer instead of heat transfer, thus it allows continuous heating during and after the ignition, varying the cooling rate and, as a consequence, the microstructure and there is also a more rapid temperature increase of the whole reaction zone. This is also expected to minimize the extension of heat affected zones.
Concerning nanostructured carbon composites, two different experimental approaches which allow the synthesis of CNT on carbon-based substrate have been used. One method exploits a barrier layer between substrate and CNTs, the other tries to grow CNTs directly on the carbon-based composite. The CNT growth is a promising approach for improving the mechanical, electrical and thermal properties of structural composites. However, this work is only a preliminary study focused on the growth process of CNT and further developments are necessary for inspecting wider issues concerning the new composite material like infiltration with the carbon matrix precursors and optimization of such proces
Microwave ignited combustion synthesis as a joining technique for dissimilar materials
No full textMicrowave energy has been exploited to ignite combustion synthesis (CS) reactions of properly designed powders mixtures, in order to rapidly reach the joining between different kinds of materials, including metals (Titanium and Inconel) and ceramics (SiC). Beside the great advantage offered by CS itself, i.e., rapid and highly localized heat generation, the microwaves selectivity in being absorbed by micrometric metallic powders and not by bulk metallic components represents a further intriguing aspect in advanced materials joining applications, namely the possibility to avoid the exposition to high temperatures of the entire substrates to be joined. Moreover, in case of microwaves absorbing substrates, the competitive microwaves absorption by both substrates and powdered joining material, leads to the possibility of adhesion, interdiffusion and chemical bonding enhancements. In this study, both experimental and numerical simulation results are used to highlight the great potentialities of microwave ignited CS in the joining of advanced materials
Sintesi assistita da microonde per ottenere leghe ad alta entropia a diverso tenore di alluminio
No full textIn questo studio si è analizzato l’effetto della variazione del contenuto di alluminio nella sintesi e microstruttura della lega ad
alta entropia di composizione: FeCoNiCrAlx, dove x può assumere i valori x=1,1.5,2,3. Il ruolo atteso dell’alluminio durane la
sintesi è di creare una fase liquida che acceleri le reazioni, che altrimenti avverrebbero unicamente allo stato solido, mentre
i rimanenti elementi comprendono almeno un elemento ferromagnetico per migliorare l’assorbimento delle microonde durante
la sintesi. Dalle caratterizzazioni effettuate si evince che all’aumentare del contenuto di alluminio si ottengono leghe
composizionalmente più omogenee, una promozione della struttura cristallina CCC e l’aumento della durezza media. La lega
equimolare FeCoNiCrAl è stata poi confrontata con la lega FeCoNiCuAl. Dalla diffrazione è possibile vedere la tendenza della
lega di sposarsi verso una struttura cristallina CFC, grazie alla presenza di rame
Plastic behaviour and cristallographic texture of alpha titanium alloys for heat resistant applications [Anisotropia ed orientamento cristallografico preferenziale di leghe di titanio alfa per impieghi a caldo]
No full textAs known, metallic materials presenting HCP crystallographic structure show a marked anisotropic behavior during plastic deformation, especially deep drawing. This attitude is due to the intrinsic asymmetry of hexagonal crystal lattice and is also depending on the c/a ratio of the cell itself. In addition to this aspect, also the tendency of materials such as titanium, magnesium and zirconium, to give rise to a preferential crystallographic orientation (texture) during the rolling phases needs to be taken into account. The most important aspects which contribute to texture formation are: nature and quantity of the alloying elements, reduction ratio during rolling, and heat treatments made on the alloys. Subject of present study are two alpha titanium alloys, specifically developed for heat resistant applications. Despite being quite similar in terms of chemical composition, oxidation resistance and field of application, these two alloys exhibit dissimilar plastic deformation mechanisms. The feature which makes the use of these materials very demanding on an industrial scale is the modification of their plastics properties, in particular plastic strain ratio (R-value), during the deformation progress. On the aforementioned alpha titanium alloys, a complete microstructural and mechanical characterization has been performed analyzing the material according to different orientation, whit the main purpose of identifying the trend of R-value toward strain. In addition to that, a study of the original texture of the two alloys has been made using different measuring methods (X-Ray diffraction, Electron Back-Scattering Diffraction). The purpose of this activity is finding a correlation between the macroscopic behavior of the alloys during deformation and their crystallographic orientation on microstructural scale, for better understanding the specific role played by the individual sliding systems and their spatial orientation on the plastic properties of the materials.As known, metallic materials presenting HCP crystallographic structure show a marked anisotropic behavior during
plastic deformation, especially deep drawing. This attitude is due to the intrinsic asymmetry of hexagonal crystal
lattice and is also depending on the c/a ratio of the cell itself. In addition to this aspect, also the tendency of materials
such as titanium, magnesium and zirconium, to give rise to a preferential crystallographic orientation (texture)
during the rolling phases needs to be taken into account. The most important aspects which contribute to texture
formation are: nature and quantity of the alloying elements, reduction ratio during rolling, and heat treatments made
on the alloys.
Subject of present study are two alpha titanium alloys, specifically developed for heat resistant applications. Despite
being quite similar in terms of chemical composition, oxidation resistance and field of application, these two alloys
exhibit dissimilar plastic deformation mechanisms. The feature which makes the use of these materials very demanding
on an industrial scale is the modification of their plastics properties, in particular plastic strain ratio (R-value),
during the deformation progress.
On the aforementioned alpha titanium alloys, a complete microstructural and mechanical characterization has been
performed analyzing the material according to different orientation, whit the main purpose of identifying the trend
of R-value toward strain. In addition to that, a study of the original texture of the two alloys has been made using
different measuring methods (X-Ray diffraction, Electron Back-Scattering Diffraction).
The purpose of this activity is finding a correlation between the macroscopic behavior of the alloys during deformation
and their crystallographic orientation on microstructural scale, for better understanding the specific role played
by the individual sliding systems and their spatial orientation on the plastic properties of the materials
Recycling of alpha-titanium technological scrap for exhaust system parts manufacturing
No full textn this paper, five different titanium alpha alloys obtained by investment casting, and recycled titanium scrap which originated from other technological operations have been studied in order to investigate their basic properties and to determine the industrial feasibility of the manufacturing of recycled titanium exhaust system parts on an industrial scale. Chemical analysis after a first and a second melting step, a complete mechanical characterization and oxidation resistance test at different temperatures have been performed. The direct influence of the alloying elements, like Si and Al, on the oxidation resistance of titanium at high temperature has been studied, in order to identify the best blended alloy for investment casting applications. An important aspect which has also been evaluated is the increase of oxygen content after remelting of the blend alloys and its impact on the mechanical properties. Results show that it is possible to use the identified blend alloys to obtain cast components suitable for applications requiring exposure at a temperature up to 700 C, and for the Si-richer blends, up to 800
Microwave assisted synthesis of Si-modified Mn25FexNi25Cu(50−x) high entropy alloys
Get PDFRapid microwave heating at 2450 MHz of metallic powders mixtures compacts was performed under Ar flux in a single mode applicator in order to produce Si-modified Mn25FexNi25Cu(50−x), (x=25, 30, 35, 40) high entropy alloys. Microwave heating was conducted in presence of a SiC auxiliary absorber, so that the compacts are subjected to both direct heating by microwave absorption and indirect heating by the auxiliary absorber. Due to the extremely rapid processing times, including the cooling stage, depletion of the most oxygen-reactive elements was moderate, considering the not perfectly protective atmosphere used. FCC solid solutions have been obtained and the role of Si is discussed as a microstructure modifier and as increaser of the microhardness
Microwave ignited combustion synthesis of metal and intermetallic matrix composites
No full textAim of this work is to present the results concerning the application of microwave assisted combustion synthesis (MACS) approach in the production of different kind of cermets and intermetallic matrix composite (IMC). Combustion synthesis allows taking advantages from the heat generated from exothermic reactions, which can derive from the synthesis of the intermetallic matrix, of the reinforcement, or both. Microwaves were used to ignite such combustion reactions exploiting their heating selectivity. The use of a single mode applicator allowed also investigating any "specific" microwave effects ascribable to separate electric and magnetic fields
Rapid microwave sintering of protective ZrO2 coatings on reactive metal powder compacts
No full textElectrophoretic deposition was used to create protective coatings of sub-micrometric ZrO2 particles on substrates made of conductive powders mixture (Ni+Al). In order to achieve the required mechanical properties, such coating requires a sintering stage. However, the rapid microwave sintering of thin zirconia layers usually requires some form of pre-heating or auxiliary heating of the material, in order to increase its loss factor. In this study, the heat released by the exothermal reactions of combustion synthesis occurring in the powders compact, is used to concurrently synthesize high-temperature rated aluminides and pre-heat and sinter the overlaying zirconia coating. Finite elements numerical simulation, fully coupling electromagnetic, heat transfer and chemical reactions application modes is used to investigate the temperature profile and power density distribution during the microwave sintering process, Experimental results show that the concurrent synthesis allows to form a thin alumina-based bond coat, which is expected to increase the high temperature resistance of the zirconia-coated aluminides
Microwave ignited Combustion synthesis of intermetallic compounds, modelling and experimental results
Get PDFThe process of Combustion synthesis (CS) is based on the highly exothermic reaction by reactants, which, if properly ignited, spontaneously turn into products. The aim of this work is to study the CS of β-NiAl formed starting from Ni and Al (1:1 at. %) powders activated by microwaves at 2.45 GHz. Numerical simulation is used to obtain data otherwise difficult to be measured experimentally and to develop a predictive model of microwave ignited and sustained CS of metal powder compacts. The simulation couples an electro-thermal model with a chemical model, required to study the exothermic reaction between powders. A simplify model was obtained and validated, neglecting volume changes, to study compositional and temperature change and reaction kinetics during the CS. It allowed to demonstrate how microwave application, during and after, synthesis could control the cooling rate of products and hence the microstructure of the newly formed intermetallics
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